Superchargers are devices for increasing the power output of internal combustion engines. They achieve this by increasing the mass of air, which is input to the cylinders, thereby increasing the combustible mass of the air fuel mixture in each cylinder above that which would be pumped by the pistons at atmospheric pressure.
Superchargers of several types are known in the industry. One type is belt driven by the engine itself and is functional whenever the engine is operating. Such superchargers are large and relatively expensive, complex and add significant weight as some use precision gearing to multiply the speed of the engine rpms to achieve speed necessary to move the amount and pressure of air. Their size limits their ability to be used in the cramped engine compartments of modern automobiles. Their complexity usually requires professional installation as well as modifications to the engine management system. A second type is a turbo supercharger. This type uses the waste exhaust gas from the engine to drive a centrifugal impeller, which compresses the air input to the engine which is on a common shaft with the compressor. A third type of supercharger is electrically driven, does not use the engine itself as its power source directly, but instead uses a separate electric motor which is powered by a battery or other DC power source.
However, electric superchargers still suffer the disadvantages of size, complexity, weight and cost. They also operate whenever the engine is running, even when such operation would not be needed and may actually be undesirable. This could result in unnecessary wear and power loss of the entire system consisting of the engine, supercharger and power source for the supercharger. One other disadvantage of known electric superchargers which use centrifugal impellers is that the impeller must be operated at very high speed, of the order of 50-80,000 revolutions per minute, and therefore requires high current input, even when the engine is operating at low power.
A requirement therefore exists for a supercharger which is relatively small, simple, inexpensive, easy to install and operates only when maximum power is required from the engine. Such occasions could be during passing another car, during emergency maneuvers, or for limited periods during automobile race events. A supercharger which meets these characteristics would have significant use because of its cost and simplicity even if it provided only a modest increase in power, since even a modest increase would be important at critical times, especially in an automotive application.